In angiographic tests based on DSA (digital subtraction angiography) and other computer images, the frequency of use of the trans-brachial artery catheterization technique is still low at present, the trans-femoral artery catheterization technique being frequently used. The reason seems to be the lack of the safety of catheter manipulation and the lack of a selective or superselective catheter manipulating technique directed to the systemic arteries.
The trans-brachial artery catheterization technique, however, has the advantage that hemostasis subsequent to a test can be effected in the state which allows the patient to walk, a fact which means that this catheterization technique is also applicable to outpatients. Thus, if said selective or superselective catheter manipulating technique is developed and its safety is confirmed, there is no doubt that such technique will play a major role in the advancement of angiographic testing.
In this connection, it is known that generally in the trans-brachial artery catheterization technique, since the catheter has to be inserted into a puncture hole formed in the thin brachial artery, a thrombus or occlusion tends to form in the brachial artery subsequently to a test. To prevent this, it is necessary to use a catheter which is as thin as possible, having a diameter less than the inner diameter of the brachial artery while ensuring blood flow even during insertion of the catheter.
Increasing blood flow in the brachial artery also serves to prevent formation of a thrombus or occlusion. In this connection, it is to be pointed out that in more than 250 cases in which I performed the technique of having each patient hold an athletic appliance in his hand and firmly squeeze it with time during insertion and manipulation of a catheter, formation of a thrombus or occlusion was not found.
Even if a thin catheter is used, frequent occurrence of excessive direct stimulus to the brachial artery or damage to the artery wall as well as bleeding during insertion or manipulation of the catheter leads to thrombus formation or occlusion; thus, these inducers must be removed before the safety of the trans-brachial artery catheterization technique can be enhanced.
Inasmuch as the trans-brachial artery catheterization technique is based on the principle of inserting the catheter into the artery and remote manipulating the catheter, it is extremely difficult both theoretically and practically to eliminate direct stimulus to the brachial artery wall or damage to the artery wall during insertion and manipulation of the catheter. This can also be said from the nature of the manipulation involved in the aforesaid catheterization technique wherein a catheter which is thinner and longer than in the case of the trans-femoral artery catheterization technique is required and has to be remote-manipulated safely and reliably by a single person.
However, it is theoretically possible to reduce, if not eliminate, the same. That is, there are two types of causes of direct stimulus to the artery wall during manipulation of the catheter. A first type is due to friction of contact between the catheter and the artery wall in a hole in the front wall region of the artery in which the catheter is inserted, and a second type is due to contact between the inner wall surface of the brachial artery and the catheter during manipulation of the catheter.
In reducing direct stimulus due to the first type of cause, methodologically it is contemplated either to increase the opening size of the hole in the front wall region of the artery beyond the outer diameter of the catheter or to use a separate catheter introducer to avoid friction of contact between the catheter and the artery wall. The method based on increasing the opening size of the hole in the front wall region of the artery beyond the outer diameter of the catheter has a high degree of danger of bleeding; therefore, in performing said trans-brachial artery catheterization technique, I make it a rule to use a catheter introducer as well.
As for reducing direct stimulus due to the second type of cause, I was able to attain this reduction by performing said trans-brachial artery catheterization technique while simultaneously using an introduction guide wire (a product from Terumo Kabushiki Kaisha: trade name, Radiofocus M) which is superior in pliability associated with remote manipulation of the catheter and which does not form a fixed bend when subjected to an external force. The simultaneous use of this guide wire enables the catheter to transmit torque in its bent state and to rotate while sliding along the inner wall surface of the brachial artery, with the result that the state of the catheter pressing the artery wall is reduced and so is direct stimulus.
While the role which the catheter introducer is expected to play is as described above, conventional articles, now commercially available, have the following problems in applying them to the trans-brachial artery catheterization technique.
A catheter introducer comprises a sheath for introducing or guiding the catheter into a puncture hole in the artery, and a dilator removably inserted through said sheath to receive an introduction guide wire for the catheter. Thus, the inner diameter of the sheath is 1 French size greater than the outer diameter of the catheter, and even if a thin catheter is purposely used, the result is the same as if a thick catheter, which is 1 French size greater, were used, thus forming a cause of impediment to blood flow in the brachial artery.
Moreover, said sheath does not have a mechanism which brings it in intimate contact with the dilator inserted therethrough. The outer diameter of the dilator is smaller than the inner diameter of the sheath, and the two parts are merely fitted together on the basis of a construction in which the two sizes do not produce a varying elastic action; therefore, an air gap, even though small, is inevitably produced in the fitting surface.
As a result, even if the sheath is thin-walled, the front end step portion of the sheath relative to the dilator forms a cause of damaging the artery wall when the introducer is inserted into the artery. The reason is that the thin wall of the sheath causes the front end step portion to crack and turn back as if burred.